Department of Bioengineering, Imperial College London, London SW7 2AZ, UK.
Philos Trans R Soc Lond B Biol Sci. 2023 Dec 4;378(1891):20220547. doi: 10.1098/rstb.2022.0547. Epub 2023 Oct 16.
Herbivores large and small need to mechanically process plant tissue. Their ability to do so is determined by two forces: the maximum force they can generate, and the minimum force required to fracture the plant tissue. The ratio of these forces determines the relative mechanical effort; how this ratio varies with animal size is challenging to predict. We measured the forces required to cut thin polymer sheets with mandibles from leaf-cutter ant workers which vary by more than one order of magnitude in body mass. Cutting forces were independent of mandible size, but differed by a factor of two between pristine and worn mandibles. Mandibular wear is thus likely a more important determinant of cutting force than mandible size. We rationalize this finding with a biomechanical analysis, which suggests that pristine mandibles are ideally 'sharp'-cutting forces are close to a theoretical minimum, which is independent of tool size and shape, and instead solely depends on the geometric and mechanical properties of the cut tissue. The increase of cutting force due to mandibular wear may be particularly problematic for small ants, which generate lower absolute bite forces, and thus require a larger fraction of their maximum bite force to cut the same plant. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.
大小草食动物都需要对植物组织进行机械加工。它们进行这种加工的能力取决于两个力：它们能产生的最大力，以及使植物组织断裂所需的最小力。这些力的比值决定了相对机械功；动物体型的这种比值变化难以预测。我们用身体质量差异超过一个数量级的切叶蚁工蚁的下颚切割薄片聚合物，测量了切割所需的力。切割力与下颚大小无关，但新的和磨损的下颚之间相差两倍。因此，下颚磨损很可能是切割力的一个比下颚大小更重要的决定因素。我们用生物力学分析来合理化这一发现，该分析表明，新的下颚具有理想的“锋利”特性——切割力接近理论最小值，该最小值与工具的大小和形状无关，而仅取决于切割组织的几何和机械特性。由于下颚磨损导致的切割力增加，对于生成的绝对咬合力较低的小型蚂蚁来说可能是一个特别大的问题，因此它们需要更大比例的最大咬合力来切割相同的植物。本文是主题为“动物的食物加工和营养吸收”的特刊的一部分。
